[project @ 2000-08-03 11:28:35 by simonmar]

Implement +RTS -C<n>, the context switch interval flag.  This was
previously advertised in the usage message, but there was a note in
the Users' Guide stating that it didn't work.  Anwyay, I'm going to
consider it a bug and backport to 4.08.1.

diff --git a/ghc/includes/Constants.h b/ghc/includes/Constants.h
index d0640f7..bc6b162 100644 (file)
--- a/ghc/includes/Constants.h
+++ b/ghc/includes/Constants.h
@@ -1,5 +1,5 @@
 /* ----------------------------------------------------------------------------
- * $Id: Constants.h,v 1.12 2000/07/26 13:27:54 simonmar Exp $
+ * $Id: Constants.h,v 1.13 2000/08/03 11:28:35 simonmar Exp $
  *
  * (c) The GHC Team, 1998-1999
  *
@@ -194,13 +194,6 @@
 #define INFO_FIRST_TAG         0
 
 /* -----------------------------------------------------------------------------
-   Context switch timing constants.
-   -------------------------------------------------------------------------- */
-
-#define CS_MAX_FREQUENCY 100              /* context switches per second */
-#define CS_MIN_MILLISECS (1000/CS_MAX_FREQUENCY)/* milliseconds per slice */
- 
-/* -----------------------------------------------------------------------------
    How much C stack to reserve for local temporaries when in the STG
    world.  Used in StgRun.S and StgCRun.c.
    -------------------------------------------------------------------------- */

diff --git a/ghc/rts/Itimer.c b/ghc/rts/Itimer.c
index 9117157..c327528 100644 (file)
--- a/ghc/rts/Itimer.c
+++ b/ghc/rts/Itimer.c
@@ -1,5 +1,5 @@
 /* -----------------------------------------------------------------------------
- * $Id: Itimer.c,v 1.15 2000/07/17 15:09:35 rrt Exp $
+ * $Id: Itimer.c,v 1.16 2000/08/03 11:28:35 simonmar Exp $
  *
  * (c) The GHC Team, 1995-1999
  *
@@ -23,6 +23,7 @@
 #endif
 
 #include "Rts.h"
+#include "RtsFlags.h"
 #include "Itimer.h"
 #include "Proftimer.h"
 #include "Schedule.h"
@@ -45,6 +46,9 @@
  
 lnat total_ticks = 0;
 
+/* ticks left before next pre-emptive context switch */
+int ticks_to_ctxt_switch = 0;
+
 static
 void
 #if defined(mingw32_TARGET_OS) || (defined(cygwin32_TARGET_OS) && !defined(HAVE_SETITIMER))
@@ -79,7 +83,11 @@ handle_tick(int unused STG_UNUSED)
   /* For threadDelay etc., see Select.c */
   ticks_since_select++;
 
-  context_switch = 1;
+  ticks_to_ctxt_switch--;
+  if (ticks_to_ctxt_switch <= 0) {
+      ticks_to_ctxt_switch = RtsFlags.ConcFlags.ctxtSwitchTicks;
+      context_switch = 1;      /* schedule a context switch */
+  }
 }
 
 
@@ -133,6 +141,7 @@ initialize_virtual_timer(nat ms)
                0,
                TIME_PERIODIC);
 # endif
+
   return 0;
 }
  

diff --git a/ghc/rts/Itimer.h b/ghc/rts/Itimer.h
index 58f4152..257d274 100644 (file)
--- a/ghc/rts/Itimer.h
+++ b/ghc/rts/Itimer.h
@@ -1,5 +1,5 @@
 /* -----------------------------------------------------------------------------
- * $Id: Itimer.h,v 1.5 2000/03/20 09:42:49 andy Exp $
+ * $Id: Itimer.h,v 1.6 2000/08/03 11:28:35 simonmar Exp $
  *
  * (c) The GHC Team 1998-1999
  *
@@ -10,6 +10,11 @@
 # define TICK_FREQUENCY   50                      /* ticks per second */
 # define TICK_MILLISECS   (1000/TICK_FREQUENCY)   /* ms per tick */
 
+/* Context switch timing constants. Context switches happen after a
+ * whole number of ticks, the default being every tick.
+ */
+#define CS_MIN_MILLISECS TICK_MILLISECS       /* milliseconds per slice */
+ 
 extern rtsBool do_prof_ticks;  /* profiling ticks on/off */
 
 nat  initialize_virtual_timer  ( nat ms );

diff --git a/ghc/rts/RtsFlags.c b/ghc/rts/RtsFlags.c
index a341fca..c86690f 100644 (file)
--- a/ghc/rts/RtsFlags.c
+++ b/ghc/rts/RtsFlags.c
@@ -1,5 +1,5 @@
 /* -----------------------------------------------------------------------------
- * $Id: RtsFlags.c,v 1.30 2000/04/19 12:42:48 simonmar Exp $
+ * $Id: RtsFlags.c,v 1.31 2000/08/03 11:28:35 simonmar Exp $
  *
  * (c) The AQUA Project, Glasgow University, 1994-1997
  * (c) The GHC Team, 1998-1999
@@ -25,6 +25,7 @@
 #include "RtsFlags.h"
 #include "RtsUtils.h"
 #include "BlockAlloc.h"
+#include "Itimer.h"            /* CS_MIN_MILLISECS */
 #include "Profiling.h"
 
 #if defined(PROFILING) 
@@ -266,7 +267,6 @@ void initRtsFlagsDefaults(void)
 
 #if defined(GRAN)
     /* ToDo: check defaults for GranSim and GUM */
-    RtsFlags.ConcFlags.ctxtSwitchTime  = CS_MIN_MILLISECS;  /* In milliseconds */
     RtsFlags.GcFlags.maxStkSize                = (1024 * 1024) / sizeof(W_);
     RtsFlags.GcFlags.initialStkSize    = 1024 / sizeof(W_);
 
@@ -402,7 +402,7 @@ usage_text[] = {
 #endif
 "  -C<secs>  Context-switch interval in seconds",
 "                (0 or no argument means switch as often as possible)",
-"                the default is .01 sec; resolution is .01 sec",
+"                the default is .02 sec; resolution is .02 sec",
 #if defined(SMP)
 "  -N<n>     Use <n> OS threads (default: 1)",
 #endif
@@ -742,7 +742,7 @@ error = rtsTrue;
                    /* Convert to milliseconds */
                    cst = (I_) ((atof(rts_argv[arg]+2) * 1000));
                    cst = (cst / CS_MIN_MILLISECS) * CS_MIN_MILLISECS;
-                   if (cst < CS_MIN_MILLISECS)
+                   if (cst != 0 && cst < CS_MIN_MILLISECS)
                        cst = CS_MIN_MILLISECS;
 
                    RtsFlags.ConcFlags.ctxtSwitchTime = cst;

diff --git a/ghc/rts/RtsFlags.h b/ghc/rts/RtsFlags.h
index 61d0a9a..12fceb2 100644 (file)
--- a/ghc/rts/RtsFlags.h
+++ b/ghc/rts/RtsFlags.h
@@ -1,5 +1,5 @@
 /* -----------------------------------------------------------------------------
- * $Id: RtsFlags.h,v 1.25 2000/04/19 12:42:48 simonmar Exp $
+ * $Id: RtsFlags.h,v 1.26 2000/08/03 11:28:35 simonmar Exp $
  *
  * (c) The GHC Team, 1998-1999
  *
@@ -76,7 +76,6 @@ struct COST_CENTRE_FLAGS {
 # define COST_CENTRES_ALL      3
 # define COST_CENTRES_XML       4
 
-    int            ctxtSwitchTicks; /* derived */
     int            profilerTicks;   /* derived */
     int            msecsPerTick;    /* derived */
 };
@@ -111,7 +110,8 @@ struct PROFILING_FLAGS {
 #endif /* DEBUG || PROFILING */
 
 struct CONCURRENT_FLAGS {
-  int ctxtSwitchTime; /* in milliseconds */
+    int ctxtSwitchTime;                /* in milliseconds */
+    int ctxtSwitchTicks;       /* derived */
 };
 
 #ifdef PAR

diff --git a/ghc/rts/Schedule.c b/ghc/rts/Schedule.c
index 05d44df..ed0389f 100644 (file)
--- a/ghc/rts/Schedule.c
+++ b/ghc/rts/Schedule.c
@@ -1,5 +1,5 @@
 /* ---------------------------------------------------------------------------
- * $Id: Schedule.c,v 1.73 2000/07/17 15:15:40 rrt Exp $
+ * $Id: Schedule.c,v 1.74 2000/08/03 11:28:35 simonmar Exp $
  *
  * (c) The GHC Team, 1998-2000
  *
@@ -850,8 +850,16 @@ schedule( void )
     
     cap->rCurrentTSO = t;
     
-    /* context switches are now initiated by the timer signal */
-    context_switch = 0;
+    /* context switches are now initiated by the timer signal, unless
+     * the user specified "context switch as often as possible", with
+     * +RTS -C0
+     */
+    if (RtsFlags.ConcFlags.ctxtSwitchTicks == 0
+       && (run_queue_hd != END_TSO_QUEUE
+           || blocked_queue_hd != END_TSO_QUEUE))
+       context_switch = 1;
+    else
+       context_switch = 0;
 
     RELEASE_LOCK(&sched_mutex);
 
@@ -1589,6 +1597,9 @@ initScheduler(void)
   context_switch = 0;
   interrupted    = 0;
 
+  RtsFlags.ConcFlags.ctxtSwitchTicks =
+      RtsFlags.ConcFlags.ctxtSwitchTime / TICK_MILLISECS;
+
 #ifdef INTERPRETER
   ecafList = END_ECAF_LIST;
   clearECafTable();